The invention is based on an apparatus for injecting a fuel-gas mixture as defined hereinafter. German Offenlegungsschrift 36 09 798 already discloses an apparatus for injecting a fuel-gas mixture, in which a fuel injection valve is surrounded by a stepped longitudinal bore of a valve holder. Downstream of an injection end of the fuel injection valve in the valve holder is a mixing line that communicates upstream, via a gas gap formed between the injection end and the longitudinal bore, with an annular gas conduit that communicates with a gas source. However, this apparatus has the disadvantage that the gas is delivered to the annular gas conduit through a single line and flows downstream into the mixing line through the gas gap. The danger thus exists that the fuel stream will be asymmetrically affected by the delivered gas, so that a fuel film forms on the walls of the mixing line. Accordingly, the formation of a maximally homogeneous fuel-gas mixture is not assured.
The size of the annular gas gap and the quality of centering of the fuel injection valve also depend on tolerances in the length and shape of both the fuel injection valve and the longitudinal bore of the valve holder.